Morphology of salivary calculi. The distribution of the inorganic component

Different hypotheses concerning the pathogenesis of salivary calculi have been postulated on the basis of their morphology. In the present study, microradiography of plane-polished ground sections of a number of salivary calculi has shown that the morphology of salivary calculi varies considerably. The commonly accepted concept that salivary calculi emanate from an inorganic nucleus, which then successively grows by the apposition of alternating shells of organic and inorganic substances, could not be established by this study, as the microradiographs show that the distribution of mineral elements varied extensively from one calculus to another. Thus, whereas some calculi exhibited a lamellar structure, others consisted largely of homogeneous, irregular layers of alternatively high and low mineral content. The lamellar structure also showed great variation, extending in some cases over the entire diameter of the calculus. Some calculi lacked the lamination in their peripheral parts whereas, in others, lamination occurred only in the most peripheral zone. The structure of the central portions also showed a varied configuration. The calculi were often built up around one or more mineralized nuclei, often centrally located, while in some cases a mineralized nucleus was lacking. This report discusses some of the significant factors in the great variation in morphological features and therefore also in the pathogenesis of salivary calculi.